Variable displacement gear pump



Dec. 28, 1948. c. E. GROSSER I VARIABLE DISPLACEMENT GEAR PUMP 2 Sheets-Sheet 1 Filed April 27, 1946 m m h Chrislfi anE Grosser B fi g y -j2?orn a. I

Dec. 28, 1948. c. E. GROSSER VARIABLE DISPLACEMENT GEAR PUMP 2' She'ets-Sheet 2 Filed April 27, 1946 llllllllll Patented Dec. 28, 1948 VARIABLE DISPLACEMENT GEAR PUIVIP Christian E. Grosser, Warwick, R. 1., assignor, by mesne assignments, to Cread Engineering and Research Company, Cranston, R. L, a corporation of Rhode Island Application April 27, 1946, Serial No. 665,440

6 Claims. (Cl. 103-120) This invention relates to variable-displacement hydraulic pumps of the gear-type and consists in improvements in the construction and method of operation thereof.

One object of the invention is to provide a hydraulic gear-pump of simple and compact construction adapted for manufacture at low cost.

Another object is to provide a gear-pump which may be readily adjusted from the outside of its casing to vary the displacement of the fluid discharged therefrom.

Another object is to provide a gear-pump adapted for various uses with its operatingparts not subject to excessive wear or deterioration during long periods of use.

Further objects of the improvement are set forth in the following specification which describes a preferred form of construction of the pump, :by way of example, as illustrated by the accompanying drawings. In the drawings:

Fig. l is an elevational view of the pump shown with a section of its casing removed to disclose the working parts therein;

Fig. 2 is a similar view showing the pump adjusted for a different displacement capacity;

Fig. 3 is a transverse sectional view of the pump taken on line 3-3 of Fig. l;

Fig. 4 is an enlarged fragmentary view of the ring-gear and the pinion driven therefrom shown in certain relation thereto;

Fig. 5 is a similarly enlarged fragmentary view of the driving pinion shown in mesh with the ring-gear in a relationship corresponding to the relationship of the driven pinion and ring-gear in Fig. 4; and

Fig. 6 is a view similar to Fig. 4, but illustrating a different relationship between the driven pinion and the ring-gear.

The present improved variable-displacement pump comprises, in general, a cylindrical casing or housing 2, a ring-gear 3 and a pair of piniongears 4 and 5 arranged with their teeth in mesh with the teeth of the ring-gear.

Referring particularly to Figs. 1 and 3, the cylindrical casing .2 is of relatively narrow width comprising two halves or sections 1 and 8 spaced the annulus or rim III to form an enclosure for the gears. A series of bolts ll extend through the peripheral portions of the sections 1 and 8 and are provided with suitable nuts I! for drawing the parts together to seat the halves of the casing snugly against the opposite faces of the annulus or rim II). If desired, gaskets, not herein shown, may be used between the engaging surfaces of the sections 1 and 8 and rim ill to provide an oil-tight joint for the parts. Certain of the bolts ll may be employed for attaching the casing to a bracket l5, shown in Figs. 1 and 2, which may be fastened to an upstanding wall or stanchion or in other cases used as a base for the pump in accordance with the position it is to occupy.

The annular insert or rim I0 is provided with two plane faces IE on the opposite sides of its interior which form parallel ways for a slidable bearing-ring I! to adapt the latter for eccentric adjustment relative to the axis of the casing. The interior face of the bearing-ring I1 is machined to provide a raceway for a series of frictionreducing elements such as the rollers 20 shown most clearly in Figs. 1 and 3. The bearingrollers 20 are mounted in a circumferential groove 2| in the periphery of the ring-gear 3 to adapt the latter to turn freely within the bearingring ll.

The bearing-ring I! may be adjusted diametrically across the interior of the casing 2 by any suitable means such as a screw-shaft 22 threaded through the side of the insert or spacing rim l0 and carrying a handwheel '25 or any other suitable manuallyor mechanically-operative element. As shown in the present drawings, the screw-shaft 22 is reduced at its inner end and provided with a boss or flange-like head 23 engaged in a slot 24 in the side of the bearing-ring I! for connecting it to slide the latter. The handwheel 25 may be fitted to the outer reduced end of the screw-shaft 22 and secured rotatively therewith by means of a set-screw 26 and nut 21.

The pinion 4 is constituted as the driving-gear of the pump, being keyed at 29 to a drive-shaft .30 journaled in suitable hearings in the opposite sections 1 and 8 of the casing 2. The drive-shaft 30 may carry a pulley, gear or other power-driven element keyed thereto or it may be connected directly to a motor or other source of power. The driven pinion 5 is mounted free to rotate on a stub-shaft 3| held in bores in the opposite faces of the sections 1 and 8 of the casing 2. The two pinions 4 and 5 are thus journaled-in spaced rela-' tionship on opposite sides of the transverse axis of the casing with the peripheries of their teeth in close contact with the cylindrical faces 32 and 33 of a separator-element or block 35 secured fast at the center of the chamber. The separator 35 is of substantially I-shape with the circular con-- tact faces '32 and 33 formed by 'concavities on its opposite sides. The separator 35 may be held fixedly at the center of the casing 2 with its concaved'faces 32 and 33 arranged concentrically of the pinions 4 and by means of a pair of pins 38 driven into holes in the section I of the casing 2, see Fig. 3.

One of the sections of the casing 2 is provided with suction and discharge openings 40 and 42, respectively, communicating with the interior of the casing 2. The suction opening 40 may be provided with a pipe 4| threaded thereinto and connectedwith a source of fluid such as oil; and, likewise, the discharge opening 42 may have a pipe 43 threaded thereinto and arranged to feed the oil to a motor or other apparatus to be driven or controlled thereby. When the driving pinion 4 is driven from a suitable source of power connected to its shaft 30 the meshing engagement of its teeth with the teeth of the ring-gear 3 will rotate the latter to drive the pinion 5 through the meshing engagement of its teeththerewith.

Referring to Figs. 4 to 6, inclusive, it will be observed that the teeth on the pinions and rin gear are of peculiar form, the teeth on both pinions 4 and 5 having a development somewhat like that of ordinary gear-teeth, but more pointed at their ends; while the teeth on the ring-gear 3 have slightly concaved working faces which merge in sharp points at their outer ends. The purpose of this peculiar and novel formation'of the teeth will be understoodmore clearly by the following explanation of the method of operation of the pump. Itwill be understood by referring to Figs. 1 and 2 that the ring-gear 3 may be adjusted diametrically with respect to the axis of the casing 2 to vary the relationship between its teeth and the teeth of the two pinions 4 and 5; it being obvious that such adjustment of the ring-gear is limited by the bottoming of the teeth of either one of the pinions between the teeth of the ring-gear as indicated at the right in Fig. 1 and at the left in Fig. 2. With the ring-gear 3 adjusted to the position shown in Fig. 1 a relatively large inter-tooth spacing is effected between the teeth of the pinion 4 and those of the ring-gear 3; whereas, the teeth on the pinion 5 will be closely inter-related to the teeth on the ring-gear 3.

Referring to Fig. 1, in the operation of the pump the volume of oiltransferred in all instances by means of the inter-tooth spaces at (C) between the teeth of the pinion 4 traveling against the concaved surface 32 is exactly equal to and balanced by the oil transferred at (D) by the teeth of the pinion 5 traveling in the opposite direction against the concaved face 33 of the separator 35. With the ring-gear 3 adjusted to the position shown in Fig. 1 the clearance space between the teeth of the pinion 4 and thoseof the ring-gear 3 is maximum at (A) and minimum at (B) where the teeth of the pinion 5 mesh closely with the teeth of the ring-gear 3. In this position of the ring-gear the delivery of the pump is equal to the volume of oil enterin the suction opening 40 and transferred at (A) minus the oil transferred at (B). Now, if the ring-gear 3 is displaced to the right the clearance space between the teeth of the pinion 4 and those of the ring 3, or at (A), is decreased while the clearance at (B) is increased with a corresponding change in the volume of oil transferred the ring-gear 3 ositioned in concentric relation be equal and no oil will be pumped.

with respect to the two pinions, that is, having its teeth in equal engagement with the teeth on both of them, the clearances at (A) and (B) will However, as motion of the ring-gear 3 is continued to the right. the clearance between the teeth of the pinion 5 and those of the ring-gear 3, that is at (B), will be increased and the clear ance between the teeth of the pinion 4 and those of the ring-gear 3 at (A) decreased to such an extent that the direction of pumping will be reversed when the ring-gear is finally adjusted to the position shown in Fig. 2; the opening 42 thereby becoming the suction inlet for the pump and the opening 42 the discharge outlet.

The present invention provides a pump of exceedingly inexpensive construction wherein the displacement can be varied by infinitely small steps from a maximum in one direction through zero to a maximum in .the opposite direction. When the present pump is used for serving power to a hydraulic motor of fixed displacement it becomes a variable-speed hydraulic transmission device similar in operation to multiple pistontype-transmissions now in use. Its applications to use for transmission devices of this type are extensive including machine tools, paper-mill equipment, wire-drawing equipment, conveyors and other light apparatus, thereby being adapted to displace conventional multiple piston-pumps of high cost heretofore undesirable where small amounts of power are involved. In other words,

the present variable displacement gear-pump provides an inexpensive variable-speed hydraulic transmission device in the small power field where cost is an important factor. Moreover, the simplicity of the present design-besides making for low cost of manufacture, results in a pump of especial compactness and light-weight while reducing wear and deterioration of its parts in comparis'on to the conventional piston-type pumps heretofore used.

While the present improved pump is herein shown as embodied in a preferred form of construction, it is to be understood that modifications may be made in the structure and arrangement of its parts without departing from the spirit or scope of the invention. Therefore, Without limiting myself in this respect, I claim: 1. A variable-displacement gear-pump comprising a casing, a ring-gear rotatable within the interior of the casing, means for adjusting the ring-gear in a direction diametrically of its axis, a pair of pinions journaled in spaced relationship within the casing with their teeth in mesh with the teeth of the ring-gear, a separator held fixedly within the casing between the pinions and provided with concave faces on its opposite sides in contact with the peripheries of the teeth on the two pinions, and suction and-discharge openings in the casing located on opposite sides of a line passing through the-axes of both of said pinions, said openings being separated from each other at all times by said pinions, said ring-gear and said separator.

2. A variable-displacement gear-pump comprising a casing having an interior chamber, a

pair of pinions journaled in spaced relationship within the chamber, a ring-gear surrounding the prising a casing having a substantially cylindrical interior chamber, a pair of toothed pinions Journaled on opposite sides of the axial center of the chamber in the casing, a separator fixed at the axial center of the chamber and provided with concaved faces in contact with the peripheries oi the teeth on the pinions, a ring-gear rotatable in the chamber of the casing with its internal teeth in mesh with the teeth of both pinions, means for displacing said ring-gear eccentrically of the axis or the chamber to vary the extent 0! centact 01 its teeth with the teeth of the differ-- ent pinions, and suction and discharge openings in the casing located on opposite sides of a line passing through the axes of both of said pinions, said openings being separated from each other at all times by said pinions, said ring-gear and said separator.

4. 'A variable-displacement gear-pump comprising a casing having an interior chamber, a pair of pinion-gears iournaled in spaced relationship in the chamber, a stationary separator ele-. ment within the chamber having concave faces in contact with the peripheries of the teeth on the pinions, a bearing slidably mounted within the chamber for displacement in eccentric relation ,to the pinions, a ring-gear rotatably mounted insaid'bearing with its internal teeth in engagement with the teeth 01' both pinions, means for adjusting the bearing to displace the ringgear in the chamber to vary the extent of en gagement of its teeth with the teeth of the two pinions, and suction and discharge openings in the casing located on opposite sides of a line passing through the axes of both oi said pinions, said openings being separated from each other at all times by said pinions, said ring-gear and said separators.

5. A variable-displacement gear-pump comprising a casing having an interior chamber'with suction and discharge openings communicating therewith, ways on the opposite walls of the chamber, a bearing siidable on said ways in the chamber, a ring-gear rotatably mounted in said bearing and formed with internal teeth, a pair of pinion-gears Journaled in opposite spaced relation within the ring-gear with their teeth in mesh with the teeth oi said ring-gear, a separating element fixedly mounted within the chamber and provided with concave faces-in contact with the peripheries oi the teeth on both pinions, and means on the outside of the casing connected to the bearing for sliding the latter to displace the ring-gear within the chamber to vary the extent of engagement between its teeth and the teeth of both pinions. said suction and discharge openings being located on opposite sides of a line extending through the axes of both of said pinions, said openings being separated from each other at all times by said pinions. said ring-gear and said separator.

- 6. A variable-displacement gear-pump comprising a casing, a ring-gear rotatable within the casing and formed with internal teeth having concave lateral working faces. a pair 01' pinions u Journaled in spacedrelationshipwithin the casing and formed with teeth having convex lateral working faces conforming to the shape 0! the teeth in the ring-gear, the teeth on both pinions meshing with the internal teeth on the ring-gear.

so a separator fixed within the casing between the pinions and provided with concave faces in contact with the peripheries of the teeth on the two pinions, means for displacing'the ring-gear relative to the pinions to vary the extent of engagement and thereby the clearance spaces between the teeth on the pinions and the teeth on the ring-gear, and suction and discharge openings in the casing located on opposite sides of a line passing through the axes of both of said pinions.

a said openings being separated from each other at all times by said pinions, said ring-gear and said separator.

CHRISTIAN E. GROSSER.

REFERENCES CITED The following references are or record in the me or this patent:

UNITED STATES PATENTS I so Number Name Date 1,093,278 Loftus --Apr. 14, 1914 1,646,615 Furness Oct. 25, 1927 1,704,704 Grant Mar. 12, 19 29 

